This application claims the priority of 197 38 620.2, filed Sep. 4, 1997, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a battery carrier for a traction battery of an electric vehicle, which is constrained against extreme movements in the case of a vehicle crash.
In order to achieve a sufficient traveling range, electric vehicles must be provided with large traction batteries, which may have a mass of several hundred kilograms. Battery fastening therefore becomes very significant. Because the body structure of an electric vehicle is comparable to that of a conventional vehicle with an internal combustion engine, the additional weight due to high battery mass adversely affects crash safety unless special measures are taken. With the same deformation resistance of the vehicle front end as in the case of the internal combustion engine vehicle, particularly in the initial phase (0--approximately 30 ms) of the crash progression which is important for the sensor system, the additional mass results in a drop of the characteristic deceleration curve. That is, in the event of a crash, the vehicle decelerates more slowly; and as a result, triggering of the belt tightening devices and of the air bags is delayed, so that the occupant restraint is impaired.
In order to solve this problem, European Patent Document EP 0 559 176 B1 discloses an arrangement in which the battery is disposed displaceably in the vehicle. That is, as the result of deceleration which occurs during a frontal impact, the battery carrier may be displaced in the direction of the longitudinal axis of the vehicle. At the same time, by means of energy absorbing devices, kinetic energy of the battery container is transmitted to the vehicle body in a controlled manner, while partially consuming energy.
In this arrangement, a free-running path is provided so that, after the impact, the battery carrier essentially runs free with respect to the vehicle body along a predetermined path. As a result, at the start of a crash, the battery mass is uncoupled from the vehicle for a short time, during which it has no influence on the characteristic deceleration curve. Because the triggering decision is made within this free-running time interval defined by the free-running path, no additional adaptation measures are required for the electric vehicle with respect to the front end structure or the triggering action in order to achieve the same occupant restraint as in the case of the internal combustion engine vehicle.
The free-running path in this case is formed by guiding devices constructed as oblong holes in which fastening screws are guided for fastening the battery carrier to the vehicle body, so that the battery container is longitudinally displaceable. Flat steel strips are provided as energy absorbing devices for braking the displacement. These strips run through narrow eyes whose width is such that they are deformed only after passing through the free-running path, for the purpose of consuming energy.
It is an object of the invention to provide an alternative to the battery carrier of the type described above.
This and other objects and advantages are achieved by the battery carrier arrangement according to the invention, in which the guiding device consists of at least one sliding tube or shaft which extends in the longitudinal direction of the vehicle body. Holding devices for fastening the battery container on the vehicle body reach around and clamp onto the sliding tube so that the battery container is held. In the event of a release and movement of the battery container, the sliding tube can be displaced relative to the holding devices in the axial direction for a limited distance.
In principle, the sliding tube can be fixed to the vehicle and the battery container can be displaceably disposed on the sliding tube by means of holding devices; or on the other hand, the sliding tube can be fastened to the battery container, with the holding devices for the sliding tube slidably fastened to the vehicle body. Mixed arrangements are also conceivable.
In a preferred embodiment sliding tubes are provided on both sides of the battery container, and can be used as holding grips during handling of the battery carrier.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.